Schaefer Marine has manufactured sailboat blocks for over 45 years.  Schaefer uses stainless steel or aluminum side cheeks on all of their blocks.  Schaefer blocks are legendary with regards to strength and longevity.  Rigging Only and RiggingAndHardware.Com can help you chose which Schaefer block is correct for your application.  Please call or e-mail if you have questions .